Olivine exposures at the central peak of Copernicus crater of the Earth's Moon have been confirmed by telescope observations and Clementine spectra data.Using these exposures as training sites,this study used a method of combining two spectral indices(950?nm/750?nm and 2000?nm/1500?nm),one maturity index(Is/FeO),and four chemical content indices(FeO,Mg,Al,Ca),through a decision tree classifier,to map olivine-rich units on the west lunar surface based on mosaicked Clementine image(500 m pixel size).Most classified olivine exposures are found inside craters or on their rays,suggesting that olivine exposures are directly associated with the impact processes.The results have been validated in several selected sites,though further validations with data from the newest missions are strongly needed.
Spectral indices from OMEGA hyperspectral data show that there are two main phyllosilicates exposed in and around Mawrth Vallis:Al phyllosilicates and Fe/Mg phyllosilicates.Detailed analysis of CRISM spectra shows that Al phyllosilicates such as montmorillonite,hydrated silica,kaolinite;Fe/Mg phyllosilicates such as nontronite,saponite,serpentine are widespread on the light-toned outcrops.Though similar stratigraphical sequences,morphologies and textures are observed on both sides of Mawrth Vallis from HiRISE images,suggesting that the geological processes that formed these units must have operated at a regional scale;the multiple endmember spectral mixture analysis(MESMA) derived mineral abundance indicates that there is a higher level of alteration in the western side relative to the eastern side.We suggest that the observed phyllosilicates,stratigraphical sequences and different levels of alteration might have been caused by sedimentary deposition processes in which the composition of the external source sediment or the local solution was different,or by a pedogenic process closely related to the leaching of abundant liquid water with different chemical properties.
A new object-oriented method has been developed for the extraction of Mars rocks from Mars rover data. It is based on a combination of Mars rover imagery and 3D point cloud data. First, Navcam or Pancam images taken by the Mars rovers are segmented into homogeneous objects with a mean-shift algorithm. Then, the objects in the segmented images are classified into small rock candidates, rock shadows, and large objects. Rock shadows and large objects are considered as the regions within which large rocks may exist. In these regions, large rock candidates are extracted through ground-plane fitting with the 3D point cloud data. Small and large rock candidates are combined and postprocessed to obtain the final rock extraction results. The shape properties of the rocks (angularity, circularity, width, height, and width-height ratio) have been calculated for subsequent geological studies.
